This invention relates to a fillet rolling tool for deep rolling journal fillets, and more particularly, the invention relates to a support tool for supporting the journal during deep rolling.
Deep rolling has been used for many years to strengthen the journal fillets of components such as engine crankshafts. The fillets are mechanically worked and plastically deformed by a rolling tool to strengthen the fillets and relieve stress in the area of the fillets. Typically, a pair of opposing work tools are used to roll the journal fillets. One tool includes a pair of rollers to support the lower portion of the journal while an upper tool containing at least one work roller is used to engage the journal fillet and mechanically work the fillet area. The upper and lower work tools are actuated towards one another using a hydraulic cylinder to apply pressure in the area of the journal fillet. The work piece, such as a crankshaft, is driven along its axis to roll the journal fillets. The work roller is subjected to several thousand pounds of force during the deep rolling process. These high rolling forces may accelerate tool fatigue in the presence of an undesirable amount of relative lateral movement between the crankshaft and tools.
It is common that the crankshaft may move laterally during the deep rolling process. As a result, the lateral motion introduces undesirable stresses that may fatigue the tools and cause then failure. To this end, several support tools have been developed to either prevent or minimize the effects of lateral movement between the support roller and the crankshaft thrust walls. One such tool incorporates a pair of projections extending radially from the support roller, which is received in the journal fillets to laterally locate the lower tool relative to the journal. The main journals of a crankshaft typically have different widths. For example, the main thrust journal of a crankshaft is typically wider than the other main journals of the crankshaft. Accordingly, a support roller having radial projections cannot be used for all of the main journals of the crankshaft. As a result, special support rollers must be made for the main thrust journal, which is costly. Another prior arrangement adapted for journal furnishing utilizes pads on the lateral portions of the support housing, which are permitted to collide with the thrust faces of the crankshaft. This arrangement is undesirable because the support tool must be specifically modified to accommodate the pads and may compromise the design and performance of the lower tool. Therefore, what is needed is a roller tool having support rollers suitable for use in supporting the crankshaft journals during deep rolling while minimizing the effects of lateral crankshaft movement.
The present invention provides a support tool for supporting a crankshaft journal during machining. The support tool includes a support housing having an opening and a support roller having a central portion received in the opening. The central portion is supported in the opening, preferably by a plurality of needle bearings, and includes opposing end portions. Opposing roller portions extend radially outwardly from each of the opposing end portions. Preferably, one of the opposing end portions is formed integrally with an end portion of the central portion, and the other opposing end portion is removably secured to the other opposing end portion. The opposing end portions have an outer cylindrical support surface for supporting a crankshaft journal. Each of the opposing roller portions include a lateral crankshaft engagement surface and an inner surface in spaced relationship from the lateral crankshaft engagement surface. The inner surfaces arranged adjacent to the support housing. An annular corner joins the outer cylindrical support surface and the lateral crankshaft engagement surface and is arranged within a tangential plane on the outer cylindrical support surface. That is, the annular corner does not extend outwardly from the outer cylindrical support surface. The support rollers are preferably constructed from a OHTS steel having a hardness in the range of approximately 60-64 Rockwell C. In this manner, the support rollers are permitted to slide a limited amount on the crankshaft journals, and the hardened lateral crankshaft engagement surfaces are permitted to contact the thrust walls of the crankshaft without damage to the support rollers or the crankshaft journal or thrust walls.
Accordingly, the present invention provides a roller tool having support rollers suitable for use in supporting the crankshaft journals during deep rolling while minimizing the effects lateral crankshaft movement.